Rosetta comes home for final Earth flyby

5½ years after lift off from French Guiana, ESA’s Rosetta comet chaser has returned home for a brief, flying visit. On the morning of 13 November, controllers at the Space Operations Centre in Darmstadt, Germany, confirmed that Rosetta had successfully completed its final Earth flyby.

Travelling at a speed of 13.34 km/s, the spacecraft swept past the planet at an altitude of 2,481 km. The closest approach took place at 08:45:40 CET, just south of the Indonesian island of Java. This fourth planetary encounter gave the 3 tonne explorer enough energy to cross the asteroid belt and rendezvous with comet Churyumov-Gerasimenko.

Rosetta may also help to solve a long-standing mystery. Over the years, some spacecraft (including Rosetta) have experienced a tiny – but unexpected - change in speed as they fly past Earth. So far, no one has come up with a good explanation.

Scientists took advantage of the flyby to turn on some of Rosetta’s instruments. Early images showed a slim crescent, gradually growing in size as the spacecraft sped Earthward. Later views showed city lights glowing in the night and swirling clouds over North America and the Pacific Ocean. Other instruments studied the planet’s atmosphere and magnetic field, as well as searching for water on the Moon.

Rosetta has now completed about 4,500 million km of its 7,100 million km journey to the comet. Earth’s final flyby boosted Rosetta’s speed by 3.6 km/s, sending the spacecraft toward the outer Solar System. The next date on its 10-year trek is a flyby of a large asteroid, named Lutetia, in July 2010. Rosetta will then go into hibernation before receiving a wake-up call in spring 2014.